All of the new instructions are still handled mostly by tablegen. I've slightly
refactored the code to drive intrinsic/instruction generation from a master
list of supported variants, so all irregularities have to be implemented in one place only.

The test generation script wmma.py has been refactored in a similar way.
I've added additional checks to verify the sanity of the set of tests generated
by the script for particular PTX and SM combination.